Connecting structures for connecting a automotive power unit including an engine and a transmission with an automotive vehicle body are generally known in the art. For example, Japanese Laid-open Utility Model Application No. 62-123421 discloses a mounting structure for connecting the power unit to the vehicle body by means of four mounting elements. Usually, in the case of an engine having a cylinder block constituted of upper and lower blocks installed together with the transmission in the engine compartment of the vehicle, both the engine and the transmission are mounted against the vehicle body through a plurality of mounting means.
In such a case, however, if the stiffness of the mounting elements is not sufficient, the vibration generated by the engine and the bending movement caused between the engine and the transmission are easily transmitted to the vehicle body, and as a result, the passengers in the vehicle feel uncomfortable engine vibration.
This is especially true in the usual case in which two side mounting means are disposed at left and right sides of the power unit as seen with respect to the crank shaft which extends in the longitudinal direction of the vehicle. Such a mounting layout is likely to make the connecting rigidity of the engine and the transmission weak, since such a layout is not strong against the moment acting toward the direction along which the connecting portion of the engine and the transmission opens. As a result, the vibration of the power unit is easily transmitted to the vehicle body.
It should be noted that the above problem is more significant in a case of engines having cylinder blocks divided into upper and lower blocks, because the connecting structure between these upper and lower blocks with the transmission case becomes too complicated to maintain sufficient stiffness in the connecting portion.